Congenital adrenal hyperplasia

We divide ambiguous genitalia into four distinct diagnostic categories, the masculinized female, the under-masculinized male, disorders of genital differentiation, and true hermaphroditism.

Let's start with the most common cause of ambiguous genitalia globally, congenital adrenal hyperplasia, or CAH, which results in a masculinized female.

I like to conceptualize the fetal adrenal gland as a complex chemical factory.

It takes raw cholesterol and pushes it down three separate assembly lines to produce three distinct products, aldosterone for salt retention, cortisol for stress response, and sex androgens like testosterone.

In CAH, a vital machine on the factory floor is broken.

That broken machine is almost always the enzyme 21-hydroxylase.

These patients are genetically normal females, 46XX, with completely normal ovaries.

But the general ambiguity is secondary to the immediate, life-threatening metabolic crisis.

It's a condition where the adrenal glands, which are glands that sit on top of the kidneys, renal, you know, adrenal glands, um, they normally produce, um, cortisol, which is a stress hormone.

But people with CAH lack an enzyme that converts a precursor into cortisol, and so that precursor actually gets shunted down the androgen pathway.

So girls with this condition, then their adrenal glands during fetal development and then later on, unless they get on hormone replacement therapy, which they do early on, but during fetal development at least, their adrenal glands are producing really high levels of androgens.

And so then you can look at what is psychology and behavior like in a girl raised as a girl but who was exposed to elevated androgens before she was born? What's the effect on psychology and behavior? And, you know, the evidence is pretty clear there that, you know, they're still more likely to be heterosexual, qu-quite likely to be heterosexual, but, you know, attracted to...

It's multifactorial.

It's not simple like in congenital, like in complete androgen insensitivity syndrome, we know it's the androgen receptor gene.

In CAH, in congenital adrenal hyperplasia, it's one of a few h- genes that affect enzymes that are necessary.

In the condition that I study, IHH, idiopathic hypogonadotropic hypogonadism, let's just say IHH, um, [laughs] that-

That makes perfect sense.

Let’s shift to the reticularis layer and congenital adrenal hyperplasia, or CAH.

This is a complex one.

It is.

Dexamethasone won’t cross-react with a lab assay, so it preserves the accuracy of the subsequent cosyntropin test.

Number six, Conn’s syndrome drives hypertension by forcing the kidneys to retain sodium and dump potassium, diagnosed definitively when the aldosterone to renin ratio exceeds twenty.

Number seven, the congenital adrenal hyperplasia one rule reflects enzymatic shunting.

If the one is not first, like 21-hydroxylase, salt wastes and blood pressure drops.

But tumors aren't the only adrenal issue.

The textbook also covers congenital adrenal hyperplasia, or CAH, in case 6.5.

This is a fascinating genetic defect, often driven by a mutation in the CYP21A2 gene.

But how does one gene mutation disrupt the whole gland?

We started with Starling coining the word hormone in 1905. unpacked the competitive binding of radioimmunoassays, and mapped out how doctors use dynamic testing.

Right, stepping on the gas with ACTH or slamming the brakes with dexamethasone to interrogate the system.

We've explored the pigmentation of Addison's, the targeted mutations in CAH, the surgical interventions for Gray's disease, and the opposing mechanisms of type 1 and type 2 diabetes.

It is a phenomenal amount of high-yield biology.